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Disappearing battery charge

 I have a 2001 Durango. My one year old battery suddenly began to lose its charge last month if the car sat for two or more days. A local repair shop determined the alternator was okay, but the battery was bad. The parts store agreed and replaced the battery under warranty. 
 A week later the new battery also went dead after the car had been parked for two days. I then took it to a Dodge dealership that kept it for over a week, but couldn’t find anything wrong. Even after being parked over the weekend, it started right up for them. 
 After getting it back home I drove it for three days. I parked it for two days, and the third morning the battery was completely dead. After charging with a trickle charger for a couple of hours the car started fine.
 I bought the car new and have kept up on all the maintenance. It’s parked in my driveway the same way for over seven years with the doors locked.
 Any good ghost hunters out there who can help me figure out what’s going on?

Auto electrical shops will have the expertise and the schematics to hunt the parasitic drain down.

Or, if you’d like, try removing all the fuses to unnecessary circuits and see if the problem goes away. If it does, you can replace them on at a time. When you get to the one that causes the problem to recur, you’ve at least found the circuit containing the drain. From there you’ll need a schematic and a multimeter, but it’ll at least get you down the right road.

If you do attack this with a meter, you need to be aware that some electronic items don’t shut down right away, so you need to wait a white (maybe twenty minutes) before starting any testing.

If you want to work on this yourself you should get a digital multimeter that can handle up to 10 amps of current. Normal current draw should be less than 50 milliamps when things are in the sleep mode. Here is a link that may help you out.

A couple hours on a trickle charger wouldn’t be enough to turn a completely dead battery into a fully charged one, that would crank the engine with no problem. I think that is the clue to focus on here. When you say the battery is completely dead, what is your basis for saying that? When it is “completely dead”, do the brake lights work for example? What about the headlights? When you turn the key to “ON” (not starting the engine), do you get the usual dash lights, and the fuel tank gauge rising?

Did you change anything electrical just before the battery started dying? New radio? An aftermarket radio improperly wired can drain the battery.